Therapeutic and prognostic role of vitamin D for COVID-19 infection: A systematic review and meta-analysis of 43 observational studies

J Steroid Biochem Mol Biol. 2021 Jul;211:105883. doi: 10.1016/j.jsbmb.2021.105883. Epub 2021 Mar 26.


Vitamin D modulates the systemic inflammatory response through interaction with immune system. As such, it has a possible protective role against the risk of respiratory tract infections and other diseases. It may be useful in particular, during COVID-19 pandemic. PubMed, the Cochrane Library, and EMBASE were searched from inception until January 31, 2021, for observational or clinical studies reporting the prognosis (and therapeutic effect) of COVID-19 infection in patients with deficient vitamin D levels. The infection rate, severity, and death from COVID-19 infection were pooled to provide an odds ratio with a 95 % confidence interval (OR 95 % CI). An OR > 1 was associated with the worst outcome in deficient compared with nondeficient patients. We assessed the association between vitamin D and risk, severity, and mortality for COVID-19 infection, through a review of 43 observational studies. Among subjects with deficient vitamin D values, risk of COVID-19 infection was higher compared to those with replete values (OR = 1.26; 95 % CI, 1.19-1.34; P < .01). Vitamin D deficiency was also associated with worse severity and higher mortality than in nondeficient patients (OR = 2.6; 95 % CI, 1.84-3.67; P < .01 and OR = 1.22; 95 % CI, 1.04-1.43; P < .01, respectively). Reduced vitamin D values resulted in a higher infection risk, mortality and severity COVID-19 infection. Supplementation may be considered as preventive and therapeutic measure.

Keywords: COVID-19; Infection; Meta-analysis; Mortality; Vitamin D3.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • COVID-19 / blood
  • COVID-19 / epidemiology*
  • COVID-19 / mortality
  • COVID-19 / prevention & control
  • Dietary Supplements*
  • Humans
  • Immunity, Innate / drug effects
  • Incidence
  • Observational Studies as Topic
  • Odds Ratio
  • Pandemics*
  • Prognosis
  • Risk
  • SARS-CoV-2 / pathogenicity*
  • Severity of Illness Index
  • Survival Analysis
  • Vitamin D / blood
  • Vitamin D / therapeutic use*
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / epidemiology*
  • Vitamin D Deficiency / mortality
  • Vitamin D Deficiency / prevention & control


  • Vitamin D